Embodiments of the inventive concepts described herein relate to a TSM rate-distortion optimizing method, encoding method and device using the same, and an image processing apparatus.
The standardization work on the HEVC (High Efficiency Video Coding) is currently in progress, and the HEVC introduces a Transform Skip Mode (TSM) to improve encoding efficiency of screen contents images that are substantially utilized for a cloud service.
A TSM encoding method is one of general encoding methods and maintains a lot of edges included in a screen contents image without performing transform (e.g., DCT or DST transform) as general encoding, thereby improving the quality of images and reducing a bit rate.
However, the HEVC does not provide an algorithm for selecting an intra-prediction mode for the TSM encoding separately. As a reference encoder of the HEVC, HM may apply a Rough Mode Decision (RMD) algorithm used at DCT-based encoding to select the intra-prediction mode for the TSM encoding.
The rough mode decision algorithm for the DCT-based encoding calculates a cost using the Hadamard transform having high correlation with the DCT transform. However, due to low correlation with the TSM encoding, the rough mode decision algorithm using the Hadamard transform is not appropriate to select the intra-prediction mode for the TSM encoding.